What happens when you clone Sarkhan, the Dragonspeaker with Sakashima the Imposter after using +1 of Sarkhan? Do you get a permanent 4/4 Sarkhan dragon? Does it turn back into regular sarkhan at the end of the turn and put one or the other into the graveyard as a state-based effect? My guess is Sakashima becomes a permanent sarkhan legendary dragon with name Sakashima the imposter, but it seemed interesting so I figured I'd ask.

As covered in the Khans of Tarkir Release Notes, a copy of Sarkhan, the Dragonspeaker will be a Sarkhan planeswalker. Copying Sarkhan only copies the card itself, not the animation effect from the original Sarkhan's ability. However, you can +1 the Sakashima-copy immediately if you like, which will net you a second Legendary Dragon for the turn, with a different name.

During the cleanup step, the original Sarkhan (and the copy, if you +1-ed it) will revert to being a planeswalker, and the planeswalker uniqueness rule will force you to put either the original or the Sakashima-copy into your graveyard as a State-Based Action.